Cardiopulmonary resuscitation (CPR) is an emergency medial procedure for victims of cardiac arrest, respiratory arrest, or the like. Ventilation is an important part of CPR. In general, ventilation contributes to assisting or replacing spontaneous breathing. To provide ventilation often more than one person is needed. If only one medical professional is available, bystanders may be unwilling or unable to assist. Furthermore, when trained medical professionals are performing CPR, they often do not ventilate properly. Rather, they hyperventilate the patient or take too long to deliver ventilation.
During CPR, ventilation is usually carried out by forcing air into the lungs of the patient. This may be referred to as overpressure ventilation. During normal breathing, however, the volume of the chest cage is expanded by muscle activity and air is pulled into the lungs from ambient.
During CPR, if a bag-valve-mask or mouth-to-mouth technique is used, ventilation may not easily be performed while compressions are ongoing. Thus, it is typically recommended to stop compressions and ventilate twice for every 30 chest compressions. Often it takes a relatively long time to deliver these ventilations. As a result, the percentage of time with compression-induced blood flow is significantly reduced.
On the other hand, if a secure airway, such as an endotracheal tube is in place, a medical profession may be able to perform ventilations while compressions are ongoing. Therefore, no ventilation pauses are needed. However, these continuous ventilations are notoriously known to be performed at much too high of rates, creating a high percentage of time with overpressure in the lungs and in the thorax. This positive lung pressure is believed to inhibit venous blood return to the heart and thus limit the effect of chest compressions. This issue is, for example, discussed in: Aufderheide T P, Lurie K G: Death by Hyperventilation: A common and life-threatening problem during cardiopulmonary resuscitation. Crit Care Med 2004; 32 (9 Suppl): S345-S351.
A device for enhancing blood flow to the heart is described in U.S. Pat. No. 6,526,973. In particular, this patent describes an impedance threshold valve device employed for creating an under pressure inside the lungs that is believed to be beneficial for enhancing venous return to the heart. While being potentially beneficial for blood flow, a prolonged negative pressure inside the lungs may have other harmful effects to a patient. First of all, the underpressure may lead to pulmonary edema and/or atelectasis. Secondly, if overpressure ventilation is not carried out at regular intervals, the reservoir of oxygen in the lungs will soon be exhausted.
Typically, during chest compressions there is a certain gas exchange due to air being pushed out of the chest and pulled back in when the chest is released. However, it has been found that the exchanged volume is much less than the typical dead volume in the upper airways. Thus, the oxygen-rich air that enters the airway in the release phase of compressions seldom reaches the lungs, but is pushed out again during the next compression. Such passive, compression-driven “ventilation” is therefore not efficient for ventilating the lungs. This is described in further detail in: Deakin C D, O'Neill J F, Tabor T. “Does compression-only cardiopulmonary resuscitation generate adequate passive ventilation during cardiac arrest? Resuscitation.” 2007 October; 75(1):53-9.
There is, therefore, a need for an improved device and method for providing pressure ventilation.